Russian President Vladimir Putin attends a local administration meeting as he visits Voronezh on Aug. 5. / AFP/Getty

by Kim Hjelmgaard, USA TODAY

by Kim Hjelmgaard, USA TODAY

Moscow formally moved Thursday to impose a ban on imports of meat, fish, milk and fruit from the United States, European Union, Australia, Canada and Norway.

The ban, effective immediately, is expected to last for one year.

The diplomatic move, following a decree signed Wednesday by Russian President Vladimir Putin to "protect Russia's security," follows the latest round of sanctions by the U.S. and EU that targeted entire sectors of the Russian economy.

The U.S. and the EU have accused Russia, which annexed Ukraine's Crimean Peninsula in March, of fomenting tensions in eastern Ukraine.

Russian Prime Minister Dmitry Medvedev said Russia was also ready to introduce protective measures in aviation, car building and other industries.

Speaking live on Russian TV, he said Russia is considering banning the transit of flights from U.S. and EU commercial airlines.

"Until the last moment, we hoped that our foreign colleagues would understand that sanctions lead to a deadlock and no one needs them," he said. "But they didn't and the situation now requires us to take retaliatory measures."

Russia is the second-largest agricultural importer after China, according to the U.S. Agriculture Department. Its imports rose from $7 billion in 2000 to $33 billion in 2008.

Separately, NATO Secretary General Anders Fogh Rasmussen is traveling to Kiev Thursday as fears of a potential Russian invasion hung over eastern Ukraine.

NATO says some 20,000 Russian combat forces have massed on the border for war games and could intervene under the pretext of helping ethnic Russian civilians caught up in what Moscow calls a "humanitarian catastrophe."

In a further unrelated development out of Russia on Thursday, a lawyer for former National Security Agency contractor Edward Snowden said the American has been granted permission to remain in Russia for three more years.

Last year, Snowden was given temporary asylum but that ran out on Aug. 1.